Recent research has suggested that the neurophysiological substrate for stereopsis is present in the visual cortex of the common cat and absent in the Siamese cat. Further evidence is needed as to whether the common and Siamese cat utilize stereoscopic cues in making visual discriminations. The relationship between these abilities and the interocular alignment in common and Siamese cats has never been systematically explored. Microelectrodes are used to explore the striate cortex in common and Siamese cats. Receptive fields, types of binocular interaction, and the range of horizontal disparities exhibited by these cells are studied. Random-dot stereograms are employed in order to determine the abilities of the common and Siamese cat to discriminate stereoscopically. If the presence of gross stereopsis is confirmed, the limits of stereopsis (stereo-acuity) will be tested using psychophysical methods and similar random-dot stimuli. These preclude the use of monocular depth cues by the animals. Objective measures of interocular alignment are utilized to determine the presence and degree of strabismus in common and Siamese cats. This method is a photographic one, adapted from clinical techniques. The information from the experiments described above will not only increase our understanding of binocular information processing in cats, but may lead to the development of clinical procedures for the treatment of binocular visual anomalies in humans, including strabismus, anisometropia, and amblyopia.